FIELD: drilling and survey, particularly special methods or apparatus for drilling.
SUBSTANCE: underground system includes drain holes, the first well extending from well drilled from ground surface, mainly from underground excavation interval start to remote end thereof. The system also has a number of side holes extending from the first well. Distance between side hole bottom to well drilled from ground surface may be selected so that it is substantially the same for all side holes to facilitate side hole drilling. Method may also involve uniting two or more drain hole systems within the boundaries of underground zone to provide uniform coverage of full underground zone area. System may additionally have a number of communicating drain hole sub-systems associated with main well drilled from ground surface to reduce ground surface area, which provides access to underground zone.
EFFECT: increased efficiency, provision of uniform coverage of full underground zone area and reduced access area.
54 cl, 10 dwg
